Gels are disperse systems comprising a colloidal solution of a liquid and a solid, having a certain dimensional stability. One function of the solid substance is to increase the viscosity of the liquid phase. For this purpose, the solid substance must be lyophilic and solvatable. Further, the solid should solvate or swell either as a micelle or as a macromolecule in the liquid phase, and the colloidal particles must form a three-dimensional network in the liquid. A large number of inorganic and organic materials have been tried for increasing the viscosity of organic liquids in such a manner.
The gel-forming action of aerosils is known (H. Bruenner, Pharm. Ind. 20 (1958), 581). According to DE 31 06 913, mixtures of finely divided silica and finely divided polyolefin fibers having a fibril structure can also be used as thickeners for organic liquids. Although these gel formers give a virtually colorless and transparent gel, the required concentration of the gel formers is very high, and the fine particles of the silica aerogels are felt on the skin, which of course is a drawback when used for cosmetic applications, among others.
Other known gel compositions contain clay minerals having a sheet structure, for example bentonites or montmorillonites of the formula (X,Y).sub.2-3 (Si,Al).sub.4 O.sub.10 (OH).sub.2 Z.sub.1/8 .cndot.nH.sub.2 O, where X is Al.sup.3+, Fe.sup.3+, Mn.sup.3+ or Cr.sup.3+, Y is Mg.sup.2+, Fe.sup.2+, Mn.sup.2+, Ni.sup.2+, Zn.sup.2+ or Li.sup.+ and Z is K.sup.+, Na.sup.+ or Ca.sup.2+. Such silicates exhibit pronounced hydrophilic properties and, with absorption of large amounts of water between the lattice planes, may swell considerably or form aqueous gels having a high viscosity.
According to EP 0 204 240, gel-forming lipophilic sheet silicates can be prepared from such hydrophilic substances by exchanging interlayer cations for quaternary ammonium ions. These "organically modified" sheet silicates can, however, often be processed to a gel only in the presence of an organic solvent, which constitutes a substantial restriction. A further property of the known gel formulation is that they have a yellow to brown or green color.
Furthermore, according to DE 37 32 265, gel formers comprising aluminum magnesium hydroxy compounds having a sheet structure are also known. A specific example is the aluminum magnesium hydroxy stearate of the formula Al.sub.5 Mg.sub.10 (OH).sub.31 (C.sub.17 H.sub.35 COO).sub.4. However, gel formation, for example with liquid paraffin, does not begin until above 100.degree. C.
Additionally, a hydrogenated castor oil (THIXCIN R from Kronos Titan) is marketed as an oleogel former. This product has the disadvantage that gel preparation must take place at 55.+-.1.degree. C., and that subsequent shearing of the gel at room temperature leads to rheodestruction.
Finally, to EP 0 156 968, reaction products of partial esters of fatty acids and polyols with .gamma.-glycidyloxypropyltrialkoxysilanes can also be used as oleogel formers. However, these gel formers undergo subsequent crosslinking, and the gel formed becomes granular with time.
Thus, a need exists for compounds which surpass the known oleogel formers in their efficiency, do not have the stated disadvantages and possess a wide range of uses.